I was wondering if the Opal was also from the same family. It looks very similar to the Golden Delicious and is one of my favorites!
I have never been a huge fan of the Golden Delicious, mainly because it's normally available too late to be good. Like you said with the Jonagolds, they have to still be a little green. Often the stores won't get golden delicious until they're ripe, at which point, they aren't crisp and the taste isn't as clean.
That's one of the reasons I don't eat Red Delicious either. It's too difficult to get good ones that aren't over-ripened, and therefore mushy.
Personally, I like Galas, Braeburn, Opal, and Fuji. Those are the main ones that I eat, but I'm happy to try other ones if they aren't too ripe.
I didn't realize that so many of the modern apples were related. As always, I appreciate the informative nature of your posts. The next time I'm at the grocery store in the produce section, I'll be a little more knowledgeable... about the apples at least. :)